I'm assuming that is the bail bond. Bail bonds aren't free, you pay a small percentage that you don't get back. So if you have no money at all, you obviously can't afford to pay the bail, but you also can't afford to get a bondsman to pay it instead.

Bail bond is typically 10% of the bail amount. And that's the bail bondsman's to keep.

So, on a $500 bail, that's $50. If you're indigent, you might not have $50.